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3.3.3 Uncovering Europe’s hidden rivers

Urban rivers are frequently culverted and diverted to enable urban development. The extent of historically covered (or culverted) rivers in some European cities is considerable. For example, there is an entire network of rivers culverted under central London (Barton 1992), many of which were once noted for their rich fisheries (Walton 1653). Other examples of covered rivers in major European cities include the River Bièvre in Paris, River Fleet in London, Ladegårdsåen in Copenhagen, and the Zenne in Brussels.

The result of covering rivers is that in many urban areas, local communities may be completely unaware of the existence of a river or a stream running beneath streets, buildings or open spaces (Wild et al 2011).  

Culverted rivers are widely considered to exhibit very low ecological integrity, due to dark or reduced light levels, habitat modifications, geomorphological changes and increased diffuse and point source pollution, especially due to misconnections into surface water sewers. The darkness and other modifications to the channel often prevent passage of fish just like weirs do (Wild et al 2011).

Awareness of the problems associated with culverted rivers has increased significantly over the last decade. For example, the London’s Lost Rivers project has documented dozens of tributaries of the Thames which flow largely underground as a subterranean tangle of unseen streams.

De-culverting (uncovering or daylighting) rivers involves opening up buried water courses and restoring them to more natural conditions. Projects can vary from the simplest form – removing the ‘roof’ of a culvert and retaining existing bank walls and natural bed material – to the major reconstruction of both bed and banks using soft-bioengineering measures and river restoration techniques (Wild et al. (2011).

De-culverted rivers and streams have less of a flood risk due to underground blockages or collapse and it is easier to spot and tackle sources of pollution when you can see the water.  People can see and enjoy the wildlife that de-culverted streams support, with knock-on positive effects for health and well-being, education and recreation.  Open rivers and streams can also help to reduce the urban heat island effect and can (and are) being used to drive regeneration in downtown areas.[1]